JP4719797B2 - Internal combustion engine operation method - Google Patents

Description

  The present invention is a method for operating an internal combustion engine driven by gaseous fuel, wherein combustion of a mixture of fuel gas and air supplied to a main combustion chamber is pre-combusted in at least one engine operating region. It is guided by ignition of a mixture of ignitable fuel and air in the room, and at that time, a mixture of fuel and air combusted by self-ignition of liquid fuel is generated in the pre-combustion chamber near the end of the compression stroke. Related to what was done.

  In at least one engine operating region, the combustion of the mixture of fuel gas and air supplied to the main combustion chamber is driven by gaseous fuel guided by the ignition of the mixture of ignitable fuel and air in the precombustion chamber An internal combustion engine operating method is known (see, for example, Patent Document 1). A homogeneous mixture of fuel and air is generated in the pre-combustion chamber, and this homogeneous mixture of fuel and air generated in the pre-combustion chamber is naturally and uniformly burned by the self-ignition process near the end of the compression stroke. . This makes it possible to keep emissions as low as possible and achieve high efficiency.

  The pre-combustion chamber combustion method is particularly applicable to gas engines that are operated in a lean burn (ie, high air / fuel ratio) mode with a certain cylinder stroke volume or higher. The advantage of starting combustion in the pre-combustion chamber rather than starting combustion directly in the main combustion chamber is that the high air / fuel ratio or low ignition energy is sufficient for toxic substances despite the effectiveness of the entire cylinder charge This means that combustion with low emissions is guaranteed.

  A mixture of fuel gas and air flows from the main combustion chamber into the precombustion chamber during the compression stroke, resulting in a combustible mixture in the precombustion chamber. Conventionally, an electric ignition system or a pilot injection system has been used to ignite the mixture of fuel gas and air. In the case of electric spark ignition, in order to obtain a mixture that is significantly richer and easier to ignite compared to the main combustion chamber at the start of combustion, still more pure fuel gas or a mixture of fuel gas and air is required. Is supplied into the pre-combustion chamber. In the case of an electric ignition system, combustion is started by a flashover of an ignition spark between the electrodes of the spark plug. On the other hand, in the case of the pilot injection method, a small amount of liquid fuel is injected into the precombustion chamber at a high pressure. The This is self-igniting at a sufficiently high compression temperature and subsequently leads to the combustion of a mixture of fuel gas and air.

  The mixture of fuel gas and air in the main combustion chamber is ignited by a flame flowing from the precombustion chamber.

  A method for optimizing the operation of an air-fuel mixture compression supercharged gas engine in which a highly compressed gaseous fuel is blown into a precombustion chamber and ignited there is known (see, for example, Patent Document 2). In this case, the blowing is performed under a pressure of about 250 to 300 bar. This requires a relatively expensive blowing system. Higher fuel compression results in additional work and hence additional efficiency reduction.

  The disadvantages of the electric ignition and pilot injection systems are that a large amount of nitrogen oxides are generated in the pre-combustion chamber, and in some cases, a considerable amount of particles that relatively increase the emission of these harmful substances is also generated. is there. On the other hand, these emission optimization techniques also have the disadvantage that the energy of the flame overflowing from the pre-combustion chamber is low, and therefore the combustion in the main combustion chamber is slow and the efficiency deteriorates. In particular, the electric ignition type technology has a further serious disadvantage that the life of the spark plug is limited.

Austrian registered utility model No.006290 German Application No. 4419429

  An object of the present invention is to provide a method for operating an internal combustion engine driven by gaseous fuel, which can achieve further improvement in efficiency and reduction in emissions.

  In order to achieve the above object, in the internal combustion engine operating method according to the present invention, in at least one engine operating region, combustion of a mixture of fuel gas and air supplied to the main combustion chamber is performed with ignitable fuel in the precombustion chamber. A mixture of fuel and air that is guided by the ignition of a mixture with air and burns by the self-ignition of liquid fuel near the end of the compression stroke in the pre-combustion chamber; In the meantime, the liquid fuel is injected into the pre-combustion chamber a plurality of times.

At this time, it is preferable that at least the first injection is performed in a region between 180 ° before ignition top dead center and immediately before the original ignition time point, and preferably at least the second injection is performed in the latter half of the compression stroke. Preferably, it is carried out in the region between 30 ° before top dead center and top dead center. In this case, the fuel amount of the first injection may be larger than the second injected fuel amount.

  By performing the initial injection in the early phase of the compression stroke, wide homogenization of the fuel / air mixture in the pre-combustion chamber is achieved. The second fuel injection in the ignition top dead center region is used for the original ignition, in which case only a very small amount of fuel is required for the ignition.

  Due to the multiple injections and the small amount of the second injection, there is only a slight heterogeneous mixture component in the precombustion chamber at the time of ignition, so that the fuel in the precombustion chamber is very rapid and It can be burned under a low generation amount of harmful substances. This, on the one hand, favors particle and NOx emissions, and on the other hand results in more energy being utilized in the main combustion chamber for faster combustion. As a result, higher efficiency can be achieved by achieving a higher average pressure.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows a cylinder 1 of an internal combustion engine with a reciprocating piston 2 driven by gaseous fuel. The mixture of fuel gas and air flows into the main combustion chamber 5 through the intake passage 3 when the intake valve 4 is opened, and is then pushed into the precombustion chamber 6 during the compression stroke. The fuel is injected into the pre-combustion chamber 6 a plurality of times by the injection device 7. At this time, the first fuel injection is performed in a region from a crank angle of 180 ° before ignition top dead center to immediately before the original ignition time. Done in By this early fuel injection, a substantially homogeneous mixture of fuel and air is formed in the precombustion chamber 6. The original ignition is realized by the second fuel injection by the injection device 7 in the ignition top dead center region. At that time, the second fuel injection amount is very small. Thereby, the emission resulting from the second injection can be kept as low as possible. However, when the combustion chamber temperature is very high, in order to avoid ignition too early, it is also preferable that the initial fuel injection amount be suppressed slightly compared to the second injection.

  The precombustion chamber 6 is in communication with the main combustion chamber 5 via one or a plurality of holes 8. By the second fuel injection, the homogeneous mixture of fuel and air in the pre-combustion chamber 6 is ignited near the end of the compression stroke, that is, immediately before the piston 2 reaches the top dead center of ignition, The entire air-fuel mixture in the precombustion chamber 6 is combusted. The wall surface of the precombustion chamber 6 may be heated by the heating device 9 and / or heat insulation so that the self-ignition process can be started reliably.

  As ignition assistance, an ignition plug and a glow plug 10 attached in the precombustion chamber 6 or the main combustion chamber 5 can be used at the time of start-up.

  Particularly rapid combustion in the precombustion chamber 6 results in a high pressure rise and a high energy flame with a very high impulse that subsequently ignites the mixture of fuel gas and air in the main combustion chamber 5. The combustion behavior in the main combustion chamber 5 depends on the movement of the flame surface as in the combustion in the precombustion chamber 6.

The method described above is particularly characterized in that it achieves a minimum emission of NOx and particles and a very high efficiency. This low emission is due to the reduced heterogeneous diesel content, resulting in very little NOx and particle formation, and even in the main combustion chamber 5 these harmful substances are also kept low by a sufficiently high air / fuel ratio. . Despite the high air-fuel ratio in the main combustion chamber 5, high-efficiency rapid combustion is ensured by the high-energy flame flowing from the pre-combustion chamber 6 into the main combustion chamber 5.
As a result, it is possible to achieve a minimum NOx and particle emission as well as a maximum efficiency.

Schematic diagram schematically showing a cylinder 1 of an internal combustion engine driven by gaseous fuel, operated by the method according to the invention.

Claims (5)

A method for operating an internal combustion engine driven by gaseous fuel comprising:
In at least one engine operating region, the combustion of the mixture of fuel gas and air supplied to the main combustion chamber (5) is guided by the ignition of the mixture of ignitable fuel and air in the precombustion chamber (6). In this case, a mixture of fuel and air combusted by self-ignition of the liquid fuel is generated in the precombustion chamber in the vicinity of the end of the compression stroke, and the liquid fuel is combusted during one operation cycle. An internal combustion engine operating method, characterized in that the fuel is injected a plurality of times into the chamber (6). 2. The internal combustion engine operating method according to claim 1, wherein at least the first injection is performed in a region between a crank angle of 180 [deg.] Before ignition top dead center and immediately before the original ignition time.   The internal combustion engine operating method according to claim 1 or 2, wherein at least the second injection is performed in the latter half of the compression stroke, preferably in a region between 30 ° before top dead center and top dead center. .   4. The internal combustion engine operating method according to claim 3, wherein the amount of fuel for the first injection is larger than the amount of fuel injected for the second time.   The method for operating an internal combustion engine according to any one of claims 1 to 4, wherein a homogeneous mixture of fuel and air is produced in the precombustion chamber (6) after the first injection.

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